Generation of needle of transversely polarized beam using complex spiral phase mask

Abstract

The intensity distribution in the focal region for the tight focusing of needle of azimuthally polarized beam with complex-spiral phase mask is studied on the basis of the vector diffraction theory. Here we report a new method that generates a needle of transversely polarized light beam with sub diffraction beam size (0.442 \(\uplambda \)) that propagates without divergence over a long distance (of about 12.6 \(\uplambda \)) in free space (NA \(=\) 0.95). The authors also expect such a light needle of transversely polarized beam may find its application when using optical materials or instruments responsive to the transversal field only.